EP0312377B1 - Method of preparing thin film composite membranes by suspension deposition, and use of such membranes - Google Patents
Method of preparing thin film composite membranes by suspension deposition, and use of such membranes Download PDFInfo
- Publication number
- EP0312377B1 EP0312377B1 EP88309634A EP88309634A EP0312377B1 EP 0312377 B1 EP0312377 B1 EP 0312377B1 EP 88309634 A EP88309634 A EP 88309634A EP 88309634 A EP88309634 A EP 88309634A EP 0312377 B1 EP0312377 B1 EP 0312377B1
- Authority
- EP
- European Patent Office
- Prior art keywords
- polymer
- membrane
- polyurea
- layer
- urea
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired - Lifetime
Links
- 239000012528 membrane Substances 0.000 title claims description 75
- 239000000725 suspension Substances 0.000 title claims description 22
- 238000000034 method Methods 0.000 title claims description 21
- 239000002131 composite material Substances 0.000 title claims description 18
- 239000010409 thin film Substances 0.000 title claims description 11
- 230000008021 deposition Effects 0.000 title description 2
- 229920000642 polymer Polymers 0.000 claims description 71
- 229920002396 Polyurea Polymers 0.000 claims description 33
- 125000003118 aryl group Chemical group 0.000 claims description 28
- 238000000926 separation method Methods 0.000 claims description 20
- JOYRKODLDBILNP-UHFFFAOYSA-N Ethyl urethane Chemical compound CCOC(N)=O JOYRKODLDBILNP-UHFFFAOYSA-N 0.000 claims description 16
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 15
- 239000000203 mixture Substances 0.000 claims description 15
- 239000002904 solvent Substances 0.000 claims description 15
- 239000004202 carbamide Substances 0.000 claims description 14
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 12
- 229910052799 carbon Inorganic materials 0.000 claims description 12
- 239000006185 dispersion Substances 0.000 claims description 9
- 238000004519 manufacturing process Methods 0.000 claims description 8
- 125000000524 functional group Chemical group 0.000 claims description 7
- 238000005373 pervaporation Methods 0.000 claims description 5
- 238000000151 deposition Methods 0.000 claims description 4
- 239000004952 Polyamide Substances 0.000 claims description 3
- 239000004642 Polyimide Substances 0.000 claims description 3
- 229920002239 polyacrylonitrile Polymers 0.000 claims description 3
- 229920002647 polyamide Polymers 0.000 claims description 3
- 229920002480 polybenzimidazole Polymers 0.000 claims description 3
- 229920001721 polyimide Polymers 0.000 claims description 3
- 229920000098 polyolefin Polymers 0.000 claims description 3
- 239000004693 Polybenzimidazole Substances 0.000 claims description 2
- 150000004945 aromatic hydrocarbons Chemical class 0.000 claims description 2
- 229920002301 cellulose acetate Polymers 0.000 claims description 2
- 230000002194 synthesizing effect Effects 0.000 claims 1
- 239000007788 liquid Substances 0.000 description 19
- 239000012466 permeate Substances 0.000 description 18
- 229920001577 copolymer Polymers 0.000 description 14
- -1 polyethylene Polymers 0.000 description 13
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Chemical compound CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 12
- 239000000463 material Substances 0.000 description 11
- 239000010408 film Substances 0.000 description 10
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 9
- 125000001931 aliphatic group Chemical group 0.000 description 9
- 229920000728 polyester Polymers 0.000 description 9
- 239000000243 solution Substances 0.000 description 9
- 241000282326 Felis catus Species 0.000 description 8
- 150000004985 diamines Chemical class 0.000 description 7
- 229910052739 hydrogen Inorganic materials 0.000 description 7
- RYHBNJHYFVUHQT-UHFFFAOYSA-N 1,4-Dioxane Chemical compound C1COCCO1 RYHBNJHYFVUHQT-UHFFFAOYSA-N 0.000 description 6
- 238000009835 boiling Methods 0.000 description 6
- 229920000570 polyether Polymers 0.000 description 6
- 239000011148 porous material Substances 0.000 description 6
- 239000000126 substance Substances 0.000 description 6
- 239000004970 Chain extender Substances 0.000 description 5
- 239000000956 alloy Substances 0.000 description 5
- 229910045601 alloy Inorganic materials 0.000 description 5
- 238000004132 cross linking Methods 0.000 description 5
- 125000005442 diisocyanate group Chemical group 0.000 description 5
- 230000004907 flux Effects 0.000 description 5
- 229930195733 hydrocarbon Natural products 0.000 description 5
- 150000002430 hydrocarbons Chemical class 0.000 description 5
- 239000005056 polyisocyanate Substances 0.000 description 5
- 229920001228 polyisocyanate Polymers 0.000 description 5
- 229920002635 polyurethane Polymers 0.000 description 5
- 239000004814 polyurethane Substances 0.000 description 5
- 230000008569 process Effects 0.000 description 5
- UPMLOUAZCHDJJD-UHFFFAOYSA-N 4,4'-Diphenylmethane Diisocyanate Chemical compound C1=CC(N=C=O)=CC=C1CC1=CC=C(N=C=O)C=C1 UPMLOUAZCHDJJD-UHFFFAOYSA-N 0.000 description 4
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 4
- ATUOYWHBWRKTHZ-UHFFFAOYSA-N Propane Chemical compound CCC ATUOYWHBWRKTHZ-UHFFFAOYSA-N 0.000 description 4
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 description 4
- 239000012510 hollow fiber Substances 0.000 description 4
- 239000003208 petroleum Substances 0.000 description 4
- 229920000768 polyamine Polymers 0.000 description 4
- 239000008096 xylene Substances 0.000 description 4
- ZWEHNKRNPOVVGH-UHFFFAOYSA-N 2-Butanone Chemical compound CCC(C)=O ZWEHNKRNPOVVGH-UHFFFAOYSA-N 0.000 description 3
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 3
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 3
- 239000004721 Polyphenylene oxide Substances 0.000 description 3
- 239000004743 Polypropylene Substances 0.000 description 3
- 150000001414 amino alcohols Chemical class 0.000 description 3
- 125000004427 diamine group Chemical group 0.000 description 3
- 239000004815 dispersion polymer Substances 0.000 description 3
- 239000000835 fiber Substances 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- VLKZOEOYAKHREP-UHFFFAOYSA-N n-Hexane Chemical compound CCCCCC VLKZOEOYAKHREP-UHFFFAOYSA-N 0.000 description 3
- DIOQZVSQGTUSAI-UHFFFAOYSA-N n-butylhexane Natural products CCCCCCCCCC DIOQZVSQGTUSAI-UHFFFAOYSA-N 0.000 description 3
- 239000003921 oil Substances 0.000 description 3
- 229920001223 polyethylene glycol Polymers 0.000 description 3
- 229920001155 polypropylene Polymers 0.000 description 3
- 229920001451 polypropylene glycol Polymers 0.000 description 3
- 229930195734 saturated hydrocarbon Natural products 0.000 description 3
- 241000894007 species Species 0.000 description 3
- 239000011550 stock solution Substances 0.000 description 3
- 150000003738 xylenes Chemical class 0.000 description 3
- BFIMMTCNYPIMRN-UHFFFAOYSA-N 1,2,3,5-tetramethylbenzene Chemical compound CC1=CC(C)=C(C)C(C)=C1 BFIMMTCNYPIMRN-UHFFFAOYSA-N 0.000 description 2
- ICLCCFKUSALICQ-UHFFFAOYSA-N 1-isocyanato-4-(4-isocyanato-3-methylphenyl)-2-methylbenzene Chemical compound C1=C(N=C=O)C(C)=CC(C=2C=C(C)C(N=C=O)=CC=2)=C1 ICLCCFKUSALICQ-UHFFFAOYSA-N 0.000 description 2
- SVONRAPFKPVNKG-UHFFFAOYSA-N 2-ethoxyethyl acetate Chemical compound CCOCCOC(C)=O SVONRAPFKPVNKG-UHFFFAOYSA-N 0.000 description 2
- PLIKAWJENQZMHA-UHFFFAOYSA-N 4-aminophenol Chemical compound NC1=CC=C(O)C=C1 PLIKAWJENQZMHA-UHFFFAOYSA-N 0.000 description 2
- 239000004215 Carbon black (E152) Substances 0.000 description 2
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 2
- 239000005057 Hexamethylene diisocyanate Substances 0.000 description 2
- UFWIBTONFRDIAS-UHFFFAOYSA-N Naphthalene Chemical compound C1=CC=CC2=CC=CC=C21 UFWIBTONFRDIAS-UHFFFAOYSA-N 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 239000004809 Teflon Substances 0.000 description 2
- 229920006362 Teflon® Polymers 0.000 description 2
- 239000001273 butane Substances 0.000 description 2
- 238000005266 casting Methods 0.000 description 2
- 150000001875 compounds Chemical class 0.000 description 2
- RRAMGCGOFNQTLD-UHFFFAOYSA-N hexamethylene diisocyanate Chemical compound O=C=NCCCCCCN=C=O RRAMGCGOFNQTLD-UHFFFAOYSA-N 0.000 description 2
- 239000001257 hydrogen Substances 0.000 description 2
- 239000012948 isocyanate Substances 0.000 description 2
- 150000002513 isocyanates Chemical class 0.000 description 2
- 150000002576 ketones Chemical class 0.000 description 2
- IJDNQMDRQITEOD-UHFFFAOYSA-N n-butane Chemical compound CCCC IJDNQMDRQITEOD-UHFFFAOYSA-N 0.000 description 2
- OFBQJSOFQDEBGM-UHFFFAOYSA-N n-pentane Natural products CCCCC OFBQJSOFQDEBGM-UHFFFAOYSA-N 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 239000002244 precipitate Substances 0.000 description 2
- 239000002243 precursor Substances 0.000 description 2
- 239000001294 propane Substances 0.000 description 2
- 239000007858 starting material Substances 0.000 description 2
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 description 2
- DVKJHBMWWAPEIU-UHFFFAOYSA-N toluene 2,4-diisocyanate Chemical compound CC1=CC=C(N=C=O)C=C1N=C=O DVKJHBMWWAPEIU-UHFFFAOYSA-N 0.000 description 2
- AUHZEENZYGFFBQ-UHFFFAOYSA-N 1,3,5-trimethylbenzene Chemical compound CC1=CC(C)=CC(C)=C1 AUHZEENZYGFFBQ-UHFFFAOYSA-N 0.000 description 1
- 239000005059 1,4-Cyclohexyldiisocyanate Substances 0.000 description 1
- VLVVSHOQIJBJAG-UHFFFAOYSA-N 1,6-diisocyanato-2,2,4,4-tetramethylhexane Chemical compound O=C=NCCC(C)(C)CC(C)(C)CN=C=O VLVVSHOQIJBJAG-UHFFFAOYSA-N 0.000 description 1
- OFLNEVYCAMVQJS-UHFFFAOYSA-N 2-n,2-n-diethylethane-1,1,1,2-tetramine Chemical compound CCN(CC)CC(N)(N)N OFLNEVYCAMVQJS-UHFFFAOYSA-N 0.000 description 1
- WJIOHMVWGVGWJW-UHFFFAOYSA-N 3-methyl-n-[4-[(3-methylpyrazole-1-carbonyl)amino]butyl]pyrazole-1-carboxamide Chemical compound N1=C(C)C=CN1C(=O)NCCCCNC(=O)N1N=C(C)C=C1 WJIOHMVWGVGWJW-UHFFFAOYSA-N 0.000 description 1
- YBRVSVVVWCFQMG-UHFFFAOYSA-N 4,4'-diaminodiphenylmethane Chemical compound C1=CC(N)=CC=C1CC1=CC=C(N)C=C1 YBRVSVVVWCFQMG-UHFFFAOYSA-N 0.000 description 1
- JRQLZCFSWYQHPI-UHFFFAOYSA-N 4,5-dichloro-2-cyclohexyl-1,2-thiazol-3-one Chemical compound O=C1C(Cl)=C(Cl)SN1C1CCCCC1 JRQLZCFSWYQHPI-UHFFFAOYSA-N 0.000 description 1
- SUTWPJHCRAITLU-UHFFFAOYSA-N 6-aminohexan-1-ol Chemical compound NCCCCCCO SUTWPJHCRAITLU-UHFFFAOYSA-N 0.000 description 1
- 239000004677 Nylon Substances 0.000 description 1
- CTQNGGLPUBDAKN-UHFFFAOYSA-N O-Xylene Chemical compound CC1=CC=CC=C1C CTQNGGLPUBDAKN-UHFFFAOYSA-N 0.000 description 1
- URLKBWYHVLBVBO-UHFFFAOYSA-N Para-Xylene Chemical group CC1=CC=C(C)C=C1 URLKBWYHVLBVBO-UHFFFAOYSA-N 0.000 description 1
- 229920002873 Polyethylenimine Polymers 0.000 description 1
- 150000001335 aliphatic alkanes Chemical class 0.000 description 1
- 150000001336 alkenes Chemical class 0.000 description 1
- 239000003849 aromatic solvent Substances 0.000 description 1
- 230000003190 augmentative effect Effects 0.000 description 1
- 125000002915 carbonyl group Chemical group [*:2]C([*:1])=O 0.000 description 1
- 150000001735 carboxylic acids Chemical class 0.000 description 1
- 238000004523 catalytic cracking Methods 0.000 description 1
- 229920002678 cellulose Polymers 0.000 description 1
- 229920003086 cellulose ether Polymers 0.000 description 1
- 238000010382 chemical cross-linking Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 238000009833 condensation Methods 0.000 description 1
- 230000005494 condensation Effects 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000004821 distillation Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000011152 fibreglass Substances 0.000 description 1
- 239000010419 fine particle Substances 0.000 description 1
- 230000008570 general process Effects 0.000 description 1
- 239000011521 glass Substances 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- NIMLQBUJDJZYEJ-UHFFFAOYSA-N isophorone diisocyanate Chemical compound CC1(C)CC(N=C=O)CC(C)(CN=C=O)C1 NIMLQBUJDJZYEJ-UHFFFAOYSA-N 0.000 description 1
- 239000003350 kerosene Substances 0.000 description 1
- 239000007791 liquid phase Substances 0.000 description 1
- 239000012229 microporous material Substances 0.000 description 1
- 229920001778 nylon Polymers 0.000 description 1
- 150000002894 organic compounds Chemical class 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- BEZDDPMMPIDMGJ-UHFFFAOYSA-N pentamethylbenzene Chemical compound CC1=CC(C)=C(C)C(C)=C1C BEZDDPMMPIDMGJ-UHFFFAOYSA-N 0.000 description 1
- 229920002492 poly(sulfone) Polymers 0.000 description 1
- 229920000162 poly(ureaurethane) Polymers 0.000 description 1
- 229920000921 polyethylene adipate Polymers 0.000 description 1
- 229920002959 polymer blend Polymers 0.000 description 1
- 238000006116 polymerization reaction Methods 0.000 description 1
- 229920005862 polyol Polymers 0.000 description 1
- 150000003077 polyols Chemical class 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 239000000047 product Substances 0.000 description 1
- 229920005604 random copolymer Polymers 0.000 description 1
- 229920005989 resin Polymers 0.000 description 1
- 239000011347 resin Substances 0.000 description 1
- 239000012465 retentate Substances 0.000 description 1
- 229920006395 saturated elastomer Polymers 0.000 description 1
- 238000001577 simple distillation Methods 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 238000007614 solvation Methods 0.000 description 1
- 238000003756 stirring Methods 0.000 description 1
- 239000000758 substrate Substances 0.000 description 1
- 238000004227 thermal cracking Methods 0.000 description 1
Images
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/36—Pervaporation; Membrane distillation; Liquid permeation
- B01D61/362—Pervaporation
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D61/00—Processes of separation using semi-permeable membranes, e.g. dialysis, osmosis or ultrafiltration; Apparatus, accessories or auxiliary operations specially adapted therefor
- B01D61/24—Dialysis ; Membrane extraction
- B01D61/246—Membrane extraction
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
- B01D63/02—Hollow fibre modules
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D63/00—Apparatus in general for separation processes using semi-permeable membranes
- B01D63/02—Hollow fibre modules
- B01D63/021—Manufacturing thereof
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0002—Organic membrane manufacture
- B01D67/0004—Organic membrane manufacture by agglomeration of particles
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D67/00—Processes specially adapted for manufacturing semi-permeable membranes for separation processes or apparatus
- B01D67/0039—Inorganic membrane manufacture
- B01D67/0048—Inorganic membrane manufacture by sol-gel transition
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/08—Hollow fibre membranes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/10—Supported membranes; Membrane supports
- B01D69/107—Organic support material
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/12—Composite membranes; Ultra-thin membranes
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/12—Composite membranes; Ultra-thin membranes
- B01D69/1213—Laminated layers
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D69/00—Semi-permeable membranes for separation processes or apparatus characterised by their form, structure or properties; Manufacturing processes specially adapted therefor
- B01D69/12—Composite membranes; Ultra-thin membranes
- B01D69/125—In situ manufacturing by polymerisation, polycondensation, cross-linking or chemical reaction
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D71/00—Semi-permeable membranes for separation processes or apparatus characterised by the material; Manufacturing processes specially adapted therefor
- B01D71/06—Organic material
- B01D71/54—Polyureas; Polyurethanes
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/08—Processes
- C08G18/10—Prepolymer processes involving reaction of isocyanates or isothiocyanates with compounds having active hydrogen in a first reaction step
-
- C—CHEMISTRY; METALLURGY
- C08—ORGANIC MACROMOLECULAR COMPOUNDS; THEIR PREPARATION OR CHEMICAL WORKING-UP; COMPOSITIONS BASED THEREON
- C08G—MACROMOLECULAR COMPOUNDS OBTAINED OTHERWISE THAN BY REACTIONS ONLY INVOLVING UNSATURATED CARBON-TO-CARBON BONDS
- C08G18/00—Polymeric products of isocyanates or isothiocyanates
- C08G18/06—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen
- C08G18/28—Polymeric products of isocyanates or isothiocyanates with compounds having active hydrogen characterised by the compounds used containing active hydrogen
- C08G18/30—Low-molecular-weight compounds
- C08G18/32—Polyhydroxy compounds; Polyamines; Hydroxyamines
- C08G18/3225—Polyamines
- C08G18/3237—Polyamines aromatic
- C08G18/3243—Polyamines aromatic containing two or more aromatic rings
-
- C—CHEMISTRY; METALLURGY
- C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
- C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
- C10G31/00—Refining of hydrocarbon oils, in the absence of hydrogen, by methods not otherwise provided for
- C10G31/11—Refining of hydrocarbon oils, in the absence of hydrogen, by methods not otherwise provided for by dialysis
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
- B01D—SEPARATION
- B01D2323/00—Details relating to membrane preparation
- B01D2323/12—Specific ratios of components used
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
- Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y10S264/00—Plastic and nonmetallic article shaping or treating: processes
- Y10S264/18—Cross-linking a thermoplastic linear foam during molding
Definitions
- the present invention relates to a method of preparing thin film composite membrances by suspension deposition, and the uses of such membranes.
- U.S. Patent 3,370,102 describes a general process for separating a feed into a permeate stream and a retentate stream and utilizes a sweep liquid to remove the permeate from the face of the membrane to thereby maintain the concentration gradient driving force.
- the process can be used to separate a wide variety of mixtures including various petroleum fractions, naphthas, oils, hydrocarbon mixtures. Expressly recited is the separation of aromatics from kerosene.
- U.S. Patent 2,958,656 teaches the separation of hydrocarbons by type, i.e. aromatic, unsaturated, saturated, by permeating a portion of the mixture through a non-porous cellulose ether membrane and removing permeate from the permeate side of the membrane using a sweep gas or liquid. Feeds include hydrocarbon mixtures, naphtha (including virgin naphtha, naphtha from thermal or catalytic cracking, etc.)
- U.S. Patent 2,930,754 teaches a method for separating hydrocarbons e.g. aromatic and/or olefins from gasoline boiling range mixtures, by the selective permeation of the aromatic through certain cellulose ester non-porous membranes. The permeated hydrocarbons are continuously removed from the permeate zone using a sweep gas or liquid.
- U.S. -A- 4,115,465 discloses the use of supported polyurethane membranes to selectively separate aromatics from mixtures with other organic compounds.
- the polyurethane membranes employed, and the preparation thereof, are stated to be known in themselves.
- the separation process uses known techniques, including pervaporation.
- the invention provides a method of producing thhin film composite membrane having a thin active polymer layer of polyurea/urethane on a porous support layer, comprising depositing the thin active layer on the support from a dispersion-suspension of polymer in solvent, the polymer being present in the dispersion-suspension at a concentration of from 0.5 to 10 wt% polymer.
- the selected thick-permeable support layer is contacted with the polymer dispersion in the dispersing solvent. This contacting is effected in such a way that only one face of the support layer is exposed to the polymer dispersion suspension.
- a flat sheet of support layer can have a quantity of polymer dispersion poured onto it.
- the non-dissolving solvent is then permitted to evaporate from the poured layer or permeate through the thick permeable support layer; in either case depositing a thin film of dense selective polymer onto the support layer.
- a thin film composite membrane comprising a thin (2 ⁇ m or less) layer of selective film in the support layer.
- the support layer can be any porous material which is insoluble in the materials to which the finished membrane will be exposed. Porous polymeric material having pores ranging from about 0.005 to about 0.5 microns can be utilized as the support is present solely as the underlying substrate upon which the active layer is deposited. The support exhibits no separation/selectivity influence in the membrane system.
- Thee upper limit of pore size is set solely by the requirement that the polymeric material to be deposited thereon from the suspension at the concentration used not pass through the pores, i.e. that the pores be smaller than the polymer particles in the dispersion. In this way a film of the polymer in the suspension dispersion will be deposited on the support.
- Typical supports can include polyamide, polyimide,polyacrylonitrile, polybenzimidazole, teflon, cellulose acetate and polyolefins such as polyethylene and polypropylene.
- the polymer concentration in the suspension-dispersion is from 0.5 to 10 wt.%, preferably about 1 to about 5%, most preferably about 2 wt% polymer in the suspension.
- the polymer suspension is produced by preparing the polymer itself in the chosen non-dissolving dispersing non-solvent.
- non-dissolving dispersing non-solvents examples include 1, 4-diozane, cellosolve acetate, tetra-hydrofuran, ketones (e.g. acetone) and aromatic solvents such as toluene or xylenes.
- the various components going into the production of the desired polymer are dissolved in an appropriate solvent and the individual solutions are mixed and permitted to react.
- Thee polymer product is insoluble in the solvent(s) in which the starting materials are dissolved thereby resulting in the production of a fine dispersion of polymer in suspension.
- polymer concentrations of only 0.5 to 10%, preferably 1-5% in the solution, the polymer forms as a fine dispersion or suspension and not a solid mass of precipitate.
- Thin film composite membranes made by the method of the invention have application in separating aromatic hydrocarbons from saturated hydrocarbons, for example, in the chemicals industry for recovering aromatics such as benzene, toluene, xylenes etc. from chemical streams and in the petroleum industry for recovering aromatics from non-aromatics in heavy feed streams such as naphtha, heavy cat naphtha, light cat gas oil, light aromatics containing streams boiling in the C5 - 150°C (300°F) range etc. This is especially the case with the preferred membranes prepared by the method of the invention.
- a urea index defined as the percentage of the total of urea and urethane groups which are urea of at least 20% but less than 100%
- an aromatic carbon content of at least 15 mole percent
- the aromatic polyurea/urethane layer is produced using an aromatic polyurea/urethane copolymer which is itself prepared by reacting dihydroxy or polyhydroxy compounds (e.g., polyethers or polyesters of about 250 to 5000 molecular weight mixtures of different molecular weight polymers of the same type, i.e. about 30:70/70:30 mixtures of an about 500 molecular wt. polyester and an about 2000 molecular wt. polyester may also be employed) with aliphatic, alkylaromatic or aromatic diisocyanates or polyisocyanates and low molecular weight chain extenders, such as diamines, polyamines or amino alcohols.
- dihydroxy or polyhydroxy compounds e.g., polyethers or polyesters of about 250 to 5000 molecular weight mixtures of different molecular weight polymers of the same type, i.e. about 30:70/70:30 mixtures of an about 500 molecular wt. polyester and an about 2000 molecular wt. polyester may also
- Polyethers or polyesters components of 500 molecular weight give membranes of highest selectivity but lower flux.
- Polyester or polyether of higher molecular weight (e.g. 2000 and higher) give membranes of lower selectivity but with increased flux.
- the ratio and molecular weight of these components used in producing the polyurea/urethane copolymer are governed by the aforementioned characteristics possessed by the membrane useful for aromatic from saturate separation.
- the copolymer produced possesses a urea index of at least 20% but less than 100%, preferably at least 30% but less than 100%, most preferably at least 40% but less than 100%.
- urea index is meant the percentage of urea groups relative to the total urea plus urethane groups in the polymer.
- the copolymer also contains at least 15 mole percent, and preferably at least 20 mole percent aromatic carbon, expressed as a percent of the total carbon in the polymer.
- DF ratio density of functional groups
- Membranes made from urethane and polyurethane polymers which do not possess the characteristics recited above are inferior for the separation of aromatics from saturates when compared to the membranes of the present invention.
- Polyurea/urethane membranes which are not aromatic i.e. contain less than at least 15 mole percent aromatic carbon expressed as a percent of the total carbon in the polymer) are inferior to the aromatic polyurea/urethane membranes which are the subject of the present invention.
- the membranes of the present invention are especially well suited for separating aromatics from saturates in heavy feeds, such as heavy cat naphtha, wherein the constituents making up the feed include, in some cases, highly complex, multi-ring, heavily substituted aromatic species.
- the thin film composite membranes are produced from a polyurea/urethane copolymer made from dihydroxy or polyhydroxy compounds, such as polyethers or polyesters of 250 to 5000 molecular weight, reacted with aliphatic alkylaromatic or aromatic diisocyanates or polyisocyanates and low molecular weight chain extenders, such as diamines, polyamines or amino alcohols.
- a polyurea/urethane copolymer made from dihydroxy or polyhydroxy compounds, such as polyethers or polyesters of 250 to 5000 molecular weight, reacted with aliphatic alkylaromatic or aromatic diisocyanates or polyisocyanates and low molecular weight chain extenders, such as diamines, polyamines or amino alcohols.
- the polyester components are prepared from aliphatic or aromatic dicarboxylic acids and aliphatic or aromatic dialcohols.
- Aliphatic dicarboxylic acids refer to those materials having the general formula HOOCRCOOH where R contains 2 to 10 carbons (and may be either a straight or branched chain configuration).
- Aromatic dicarboxylic acids refer to those materials having the general structure HOOCRCOOH where R is: wherein R' and R" may be the same or different and are selected from the group consisting of H and C1-C5 carbons or C6H5 and combinations thereof, and n is 0 to 4. It is to be understood that in the above formula each R' or R" may itself represent a mixture of H, C1-C5 or C6H5.
- Dialcohols have the general structure HOROH where R may be where n is 1 to 10, preferably 4 to 6, and R' is H, C1 to C5 or C6H5 or where R', R" and n are defined in the same manner as for the aromatic dicarboxylic acids.
- the diisocyanates are preferably aromatic diisocyanates having the general structure: wherein R' and R" are the same or different and are selected from the group consisting of H, C1-C5 and C6H5 and n ranges from 0 to 4.
- Diamine chain extenders have the general formula H2NRNH2 where R includes aliphatic and aromatic moieties such as ⁇ (CH2) n ⁇ VII where n is 1 to 10.
- diamine chain extenders of the formula: where R' and R" are the same or different and are selected from the group consisting of H or Cl or a C1 to C5 or C6H5 and n ranges from 0 to 4.
- polyether polyols useful in the present invention as polymer precursors are polyethylene glycols, (PEG), polypropylene glycol (PPG), polytetramethylene glycol, PEG/PPG random copolymers, etc. having molecular weights ranging from about 250 to 4000.
- Aliphatic diisocyanates which may be utilized are exemplified by hexamethylene diisocyanate (HDI), 1,6-diisocyanato-2,2,4,4-tetramethylhexane (TMDI), 1,4-cyclohexanyl diisocyanate (CHDI), isophorone diisocyanate (IPDI), while useful alkylaromatic diisocyanates are exemplified by toluene diisocyanate (TDI) and bitolylene diisocyanate (TODI).
- Aromatic diisocyanates are exemplified by 4,4' diisocyanato diphenyl methane (MDI).
- Polyisocyanates are exemplified by polymeric MDI (PMDI) and carbodiimide modified MDI.
- Useful polyamines are exemplified by polyethyleneimines and 2,2',2" triaminotriethylamine.
- Useful amino alcohols are exemplified by 6-aminohexanol, 4-aminophenol, 4-amino-4'-hydroxydiphenylmethane.
- the highly aromatic polyurea layer is prepared by reacting together aliphatic, alkylaromatic or aromatic diisocyanates or polyisocyanates with diamines or polyamines.
- aliphatic alkylaromatic or aromatic carboxylic acids can be reacted with the aliphatic, alkylaromatic or aromatic diisocyanates or polyisocyanates to produce the polyurea polymer.
- mixtures of the aforesaid materials can be used to produce a complex polyurea polymer mixture.
- the diisocyanates are preferably aromatic diisocyanates having the general structure: wherein R' and R" are the same or different and are selected from the group consisting of H, C1-C5 and C6H5 and n ranges from 0 to 4.
- Diamine useful in the production of urea polymers have the general formula H2NRNH2 where R includes aliphatic and aromatic moieties such as ⁇ (CH2) n ⁇ VII where n is 1 to 10.
- diamine chain extenders of the formula: where R' and R" are the same or different and are selected from the group consisting of H or a C1 to C5 or C6H5 and n ranges from 0 to 4.
- the polyurea polymer When combining the isocyanates with the diamines, or similarly the carboxylic acids with the isocyanates to produce the polyurea polymer it is preferred that they be combined such that the total aromatic carbon content of the resulting polyurea polymer be 86% or less, preferably 50 to 75%. This is so since polyurea polymers with very high aromatic carbon content tend to be glassy rather than elastomeric in nature and in the practice of the present invention it is desirable for the polyurea membrane to be elastomeric in nature at the temperatures employed in the aromatics saturates separation process.
- the polyurea polymer produced will generally have a molecular weight ranging from about 30,000 to about 150,000, preferably about 50,000 to about 100,000.
- the maximum molecular weight in reality is set by the necessity of dissolving the polyurea polymer in a solvent in order to facilitate membrane fabrication. Since the higher molecular weight polymers are more difficult to dissolve in any given solvent system, solvation is typically augmented by the application of heat. Since it is a desirable characteristic of these polyurea membranes that they be temperature resistant, it is generally true that the higher molecular weight polymers are preferred for the production of membranes.
- crosslinking practiced after the polyurea membrane has been produced can be accomplished by employing thermal or chemical means familiar to the art.
- Chemical crosslinking is accomplished by adding formaldehyde or additional diisocyanates, said crosslinking techniques being familiar to those skilled in the art.
- Membrane thermal stability is also affected by the degree of aromaticity of the polymer and by the degree of hydrogen bonding.
- polymer aromaticity is generally set at the time of polymerization and since high aromaticity produces a membrane of a glassy nature, it is apparent that the simplest way in which to produce high temperature stable membranes involves the post crosslinking step.
- the components going to make up the individual polymers are those recited above.
- the ratio of polyurea polymer to polyurethane polymer is in the range about 5 to about 95 wt% polyurea, preferably about 10 to about 90 wt% polyurea, most preferably about 25 to about 75 wt% polyurea.
- the composite membrane consisting of polyurea polymer and polyurea/urethane copolymer
- the components used to produce the polymer and copolymer are as recited above.
- the ratio of polyurea polymer to polyurea/urethane copolymer is in the range 10 to 90, preferably 25 to 75.
- the solvent employed is one in which the copolymer polymer, polymer alloy precursors are soluble but in which the polymer, copolymer or polymer alloys will precipitate to form a dispersion of fine particles but which will not dissolve or otherwise unduly weaken the thick, porous support layer upon which the dispersion is deposited.
- solvent examples include 1,4-dioxane, ketones (e.g. acetone, methyl ethyl ketone), aromatics (e.g. toluene, xylenes) cellosolve acetate, tetrahydrofuran.
- ketones e.g. acetone, methyl ethyl ketone
- aromatics e.g. toluene, xylenes
- cellosolve acetate examples of such solvent include 1,4-dioxane, ketones (e.g. acetone, methyl ethyl ketone), aromatics (e.g. toluene, xylenes) cellosolve acetate, tetrahydrofuran.
- useful support layer materials include, polyolefins such as polyethylene, polypropylene etc., teflon, polyesters, nylon, non woven fiberglass, polyimides, polyamides, polysulfones, polyacrylonitriles, and polybenzimidazoles.
- These supports can be of any imaginable physical shape including sheets, tubes, fibers etc.
- the thin active layer may be deposited on either the inner or outer surface of such tube or hollow fiber support.
- the feed to be separated preferably will be contacted with the thin active layer face of the composite membrane.
- the composite membrane Due to the extreme thinness of the selective polymer, copolymer or polymer alloy layer the composite membrane exhibits extremely high flux while maintaining a very high level of selectivity.
- the thin film composite membranes are useful for the separation of aromatics from saturates in petroleum and chemical streams, and have been found to be particularly useful for the separation of large substituted aromatics from saturates as are encountered in heavy cat naphtha streams.
- Other aromatics containing streams which are suitable feeds for separation are intermediate cat naphtha streams boiling in the 93°C-150°C (200-320°F) range, light aromatics/saturates streams boiling in the C5-150°C (C5-300°F) range, light cat cycle oil boiling in the 205-343°C (400-650°F) range as well as streams containing benzene, toluene, xylene or other aromatics typically encounter in chemical plant processes.
- the separation techniques which may successfully employ the membranes of the present invention include perstraction and pervaporation.
- Perstraction involves the selective dissolution of particular components contained in a mixture into the membrane, the diffusion of those components through the membrane and the removal of the diffused components from the downstream side of the membrane by use of a liquid sweep stream.
- aromatics In the perstractive separation of aromatics from saturates in petroleum or chemical streams (particularly heavy cat naphtha streams) the aromatic molecules present in the feed-stream dissolve into the membrane film due to similarities between the membrane solubility parameter and those of the aromatic species in the feed. The aromatics then permeate (diffuse) through the membrane and are swept away by a sweep liquid which is low in aromatics content. This keeps the concentration of aromatics at the permeate side of the membrane film low and maintains the concentration gradient which is responsible for the permeation of the aromatics through the membrane.
- the sweep liquid is low in aromatics content so as not to itself decrease the concentration gradient.
- the sweep liquid is preferably a saturated hydrocarbon liquid with a boiling point much lower or much higher than that of the permeated aromatics. This is to facilitate separation, as by simple distillation. Suitable sweep liquids, therefore, would include, for example, C3 to C6 saturated hydrocarbons and lube basestocks (C15-C20).
- the perstraction process is run at any convenient temperature, preferably as low as possible.
- Pervaporation by comparison, is run at generally higher temperatures than perstraction and relies on vacuum on the permeate side to evaporate the permeate from the surface of the membrane and maintain the concentration gradient driving force which drives the separation process.
- perstraction the aromatic molecules present in the feed dissolve into the membrane film, migrate through said film and reemerge on the permeate side under the influence of a concentration gradient.
- Pervaporative separation of aromatics from saturates can be performed at a temperature of about 25°C for the separation of benzene from hexane but for separation of heavier aromatic/saturate mixtures, such as heavy cat naphtha, higher temperature of at least 80°C and higher, preferably at least 100°C and higher, more preferably 120°C and higher should be used, the maximum upper limit being that temperature at which either the membrane is physically damaged. Vacuum on the order of 1-50 mm Hg is pulled on the permeate side. The vacuum stream containing the permeate is cooled to condense out the highly aromatic permeate. Condensation temperature should be below the dew point of the permeate at a given vacuum level.
- the membrane itself may be in any convenient form utilizing any convenient module design.
- sheets of membrane material may be used in spiral wound or plate and frame permeation cell modules.
- Tubes and hollow fibers of membranes may be used in bundled configurations with either the feed or the sweep liquid (or vacuum) in the internal space of the tube or fiber, the other material obviously being on the other side.
- the membrane is used in a hollow fiber configuration with the then active layer in the outer surface. Feed is introduced on the exterior side of the fiber, the sweep liquid flowing on the inside of the hollow fiber to sweep away the permeated highly aromatic species, thereby maintaining the desired concentration gradient.
- the sweep liquid, along with the aromatics contained therein, is passed to separation means, typically distillation means, however, if a sweep liquid of low enough molecular weight is used, such as liquefied propane or butane, the sweep liquid can be permitted to simply evaporate, the liquid aromatics being recovered and the gaseous propane or butane (for example) being recovered and reliquefied by application of pressure or lowering of temperature.
- a stock solution was prepared from this prepolymer as follows: three point three nine (3.39) grams of the above prepolymer was added to 42.785 grams of 1,4-dioxane to produce a solution containing 7.34 wt.% prepolymer. Exactly 3.00 grams of this stock solution (0.0000906 moles of prepolymer) were placed into a 25 ml bottle.
- a second stock solution containing a diamine was prepared as follows. Exactly 0.746 grams of 4,4′-diamino-diphenyl methane (MDA) were added to 8.3641 grams of 1,4-dioxane and dissolved forming a solution of 0.884 wt% diamine.
- MDA 4,4′-diamino-diphenyl methane
- a thin film composite membrane was formed as follows. A piece of polypropylene microporous material (Celgard 2500) having an approximate pore size of 0.04 micron was clamped into a frame so that only one side would be exposed to the coating suspension. The 1.98 wt% suspension from Example 1 was poured onto the Celgard and allowed to stand for approximately one minute; whereupon it was poured off. The membrane was placed in a vertical position to allow excess suspension to run off. The procedure was repeated a second time after the dioxane had evaporated from the first application. Contact time for the second application was only 30 seconds. The film was allowed to dry overnight.
- Polypropylene microporous material (Celgard 2500) having an approximate pore size of 0.04 micron was clamped into a frame so that only one side would be exposed to the coating suspension.
- the 1.98 wt% suspension from Example 1 was poured onto the Celgard and allowed to stand for approximately one minute; whereupon it was poured off.
- the membrane was placed in
- a perstraction test was carried out in the following manner. Approximately 350 ml of model feed A was placed into the right hand side of the apparatus shown in the attached figure. The membrane to be tested was then clamped between this section and the sweep chamber which was approximately 3 mm deep. The coated side was positioned facing the sweep chamber. The feed was stirred magnetically and heated to the desired temperature. Sweep liquid was distilled from the permeate receiver and recirculated by gravity through the sweep chamber thus carrying away permeate. The sweep liquid was typically chosen to be an alkane that was much lighter than the feed for ease of separation.
- a dense film membrane of the same polymer composition was prepared in solution in dimethylformamide and cast onto a glass plate using a casting knife.
- the thickness of this membrane as measured by SEM was 11.5 ⁇ m.
- the membrane that is prepared by the process of the current invention has seven times the flux at the same selectivity as one prepared from a true solution.
- the active layer of the composite membrane of Example 2 was about 2 ⁇ by SEM.
Description
- The present invention relates to a method of preparing thin film composite membrances by suspension deposition, and the uses of such membranes.
- The use of membranes to separate aromatics from saturates has long been pursued by the scientific and industrial community and is the subject of numerous patents.
- U.S. Patent 3,370,102 describes a general process for separating a feed into a permeate stream and a retentate stream and utilizes a sweep liquid to remove the permeate from the face of the membrane to thereby maintain the concentration gradient driving force. The process can be used to separate a wide variety of mixtures including various petroleum fractions, naphthas, oils, hydrocarbon mixtures. Expressly recited is the separation of aromatics from kerosene.
- U.S. Patent 2,958,656 teaches the separation of hydrocarbons by type, i.e. aromatic, unsaturated, saturated, by permeating a portion of the mixture through a non-porous cellulose ether membrane and removing permeate from the permeate side of the membrane using a sweep gas or liquid. Feeds include hydrocarbon mixtures, naphtha (including virgin naphtha, naphtha from thermal or catalytic cracking, etc.)
U.S. Patent 2,930,754 teaches a method for separating hydrocarbons e.g. aromatic and/or olefins from gasoline boiling range mixtures, by the selective permeation of the aromatic through certain cellulose ester non-porous membranes. The permeated hydrocarbons are continuously removed from the permeate zone using a sweep gas or liquid. - U.S. -A- 4,115,465 discloses the use of supported polyurethane membranes to selectively separate aromatics from mixtures with other organic compounds. The polyurethane membranes employed, and the preparation thereof, are stated to be known in themselves. The separation process uses known techniques, including pervaporation.
- In one aspect, the invention provides a method of producing thhin film composite membrane having a thin active polymer layer of polyurea/urethane on a porous support layer, comprising depositing the thin active layer on the support from a dispersion-suspension of polymer in solvent, the polymer being present in the dispersion-suspension at a concentration of from 0.5 to 10 wt% polymer.
- The selected thick-permeable support layer is contacted with the polymer dispersion in the dispersing solvent. This contacting is effected in such a way that only one face of the support layer is exposed to the polymer dispersion suspension. Thus, a flat sheet of support layer can have a quantity of polymer dispersion poured onto it. The non-dissolving solvent is then permitted to evaporate from the poured layer or permeate through the thick permeable support layer; in either case depositing a thin film of dense selective polymer onto the support layer.
- In thisway a thin film composite membrane is produced, comprising a thin (2 µm or less) layer of selective film in the support layer.
- The support layer can be any porous material which is insoluble in the materials to which the finished membrane will be exposed. Porous polymeric material having pores ranging from about 0.005 to about 0.5 microns can be utilized as the support is present solely as the underlying substrate upon which the active layer is deposited. The support exhibits no separation/selectivity influence in the membrane system. Thee upper limit of pore size is set solely by the requirement that the polymeric material to be deposited thereon from the suspension at the concentration used not pass through the pores, i.e. that the pores be smaller than the polymer particles in the dispersion. In this way a film of the polymer in the suspension dispersion will be deposited on the support.
- Typical supports can include polyamide, polyimide,polyacrylonitrile, polybenzimidazole, teflon, cellulose acetate and polyolefins such as polyethylene and polypropylene.
- The polymer concentration in the suspension-dispersion is from 0.5 to 10 wt.%, preferably about 1 to about 5%, most preferably about 2 wt% polymer in the suspension. The polymer suspension is produced by preparing the polymer itself in the chosen non-dissolving dispersing non-solvent.
- Examples of non-dissolving dispersing non-solvents are 1, 4-diozane, cellosolve acetate, tetra-hydrofuran, ketones (e.g. acetone) and aromatic solvents such as toluene or xylenes.
- Thus, the various components going into the production of the desired polymer are dissolved in an appropriate solvent and the individual solutions are mixed and permitted to react. Thee polymer product is insoluble in the solvent(s) in which the starting materials are dissolved thereby resulting in the production of a fine dispersion of polymer in suspension. With polymer concentrations of only 0.5 to 10%, preferably 1-5% in the solution, the polymer forms as a fine dispersion or suspension and not a solid mass of precipitate.
- Thin film composite membranes made by the method of the invention have application in separating aromatic hydrocarbons from saturated hydrocarbons, for example, in the chemicals industry for recovering aromatics such as benzene, toluene, xylenes etc. from chemical streams and in the petroleum industry for recovering aromatics from non-aromatics in heavy feed streams such as naphtha, heavy cat naphtha, light cat gas oil, light aromatics containing streams boiling in the C₅ - 150°C (300°F) range etc. This is especially the case with the preferred membranes prepared by the method of the invention.
- The polyurea/urethane layer which is superior in separating aromatics from non-aromatics is distinguished by possessing a urea index, defined as the percentage of the total of urea and urethane groups which are urea of at least 20% but less than 100%, an aromatic carbon content of at least 15 mole percent, a functional group density of at least 10 per 1000 grams of polymer and a C=O/NH ratio of less than 8.
- The aromatic polyurea/urethane layer is produced using an aromatic polyurea/urethane copolymer which is itself prepared by reacting dihydroxy or polyhydroxy compounds (e.g., polyethers or polyesters of about 250 to 5000 molecular weight mixtures of different molecular weight polymers of the same type, i.e. about 30:70/70:30 mixtures of an about 500 molecular wt. polyester and an about 2000 molecular wt. polyester may also be employed) with aliphatic, alkylaromatic or aromatic diisocyanates or polyisocyanates and low molecular weight chain extenders, such as diamines, polyamines or amino alcohols. The choice of the molecular weight of the polyether or polyester component is a matter or compromise. Polyethers or polyesters components of 500 molecular weight give membranes of highest selectivity but lower flux. Polyester or polyether of higher molecular weight (e.g. 2000 and higher) give membranes of lower selectivity but with increased flux. Thus, the choice of the single molecular weight or blend is a matter of choice and compromise between selectivity and flux. The ratio and molecular weight of these components used in producing the polyurea/urethane copolymer are governed by the aforementioned characteristics possessed by the membrane useful for aromatic from saturate separation. The copolymer produced possesses a urea index of at least 20% but less than 100%, preferably at least 30% but less than 100%, most preferably at least 40% but less than 100%. By urea index is meant the percentage of urea groups relative to the total urea plus urethane groups in the polymer. The copolymer also contains at least 15 mole percent, and preferably at least 20 mole percent aromatic carbon, expressed as a percent of the total carbon in the polymer. The copolymer also possesses a particular density of functional groups (DF ratio) defined as the total of C=O+NH per 1000 grams of polymer, the density of functional group being greater than 10, preferably greater than 12. Finally, to insure that the functional groups are not mostly carbonyl, the C=O/NH ratio is less than 8 and preferably less than 5.0. This insures that there is sufficient hydrogen bonding within the polymer, resulting in strong polymer chain interactions and high selectivity.
- Membranes made from urethane and polyurethane polymers which do not possess the characteristics recited above are inferior for the separation of aromatics from saturates when compared to the membranes of the present invention. Polyurea/urethane membranes which are not aromatic (i.e. contain less than at least 15 mole percent aromatic carbon expressed as a percent of the total carbon in the polymer) are inferior to the aromatic polyurea/urethane membranes which are the subject of the present invention.
- The membranes of the present invention are especially well suited for separating aromatics from saturates in heavy feeds, such as heavy cat naphtha, wherein the constituents making up the feed include, in some cases, highly complex, multi-ring, heavily substituted aromatic species.
- As previously stated, the thin film composite membranes are produced from a polyurea/urethane copolymer made from dihydroxy or polyhydroxy compounds, such as polyethers or polyesters of 250 to 5000 molecular weight, reacted with aliphatic alkylaromatic or aromatic diisocyanates or polyisocyanates and low molecular weight chain extenders, such as diamines, polyamines or amino alcohols.
- The polyester components are prepared from aliphatic or aromatic dicarboxylic acids and aliphatic or aromatic dialcohols. Aliphatic dicarboxylic acids refer to those materials having the general formula HOOCRCOOH where R contains 2 to 10 carbons (and may be either a straight or branched chain configuration). Aromatic dicarboxylic acids refer to those materials having the general structure HOOCRCOOH where R is:
wherein R' and R" may be the same or different and are selected from the group consisting of H and C₁-C₅ carbons or C₆H₅ and combinations thereof, and n is 0 to 4. It is to be understood that in the above formula each R' or R" may itself represent a mixture of H, C₁-C₅ or C₆H₅. -
-
- Diamine chain extenders have the general formula H₂NRNH₂ where R includes aliphatic and aromatic moieties such as
―(CH₂)n― VII
where n is 1 to 10. -
- Examples of the polyether polyols useful in the present invention as polymer precursors are polyethylene glycols, (PEG), polypropylene glycol (PPG), polytetramethylene glycol, PEG/PPG random copolymers, etc. having molecular weights ranging from about 250 to 4000. Aliphatic diisocyanates which may be utilized are exemplified by hexamethylene diisocyanate (HDI), 1,6-diisocyanato-2,2,4,4-tetramethylhexane (TMDI), 1,4-cyclohexanyl diisocyanate (CHDI), isophorone diisocyanate (IPDI), while useful alkylaromatic diisocyanates are exemplified by toluene diisocyanate (TDI) and bitolylene diisocyanate (TODI). Aromatic diisocyanates are exemplified by 4,4' diisocyanato diphenyl methane (MDI). Polyisocyanates are exemplified by polymeric MDI (PMDI) and carbodiimide modified MDI. Useful polyamines are exemplified by polyethyleneimines and 2,2',2" triaminotriethylamine. Useful amino alcohols are exemplified by 6-aminohexanol, 4-aminophenol, 4-amino-4'-hydroxydiphenylmethane.
- Similarly the highly aromatic polyurea layer is prepared by reacting together aliphatic, alkylaromatic or aromatic diisocyanates or polyisocyanates with diamines or polyamines. Similarly aliphatic alkylaromatic or aromatic carboxylic acids can be reacted with the aliphatic, alkylaromatic or aromatic diisocyanates or polyisocyanates to produce the polyurea polymer. Furthermore, mixtures of the aforesaid materials can be used to produce a complex polyurea polymer mixture.
-
- Diamine useful in the production of urea polymers have the general formula H₂NRNH₂ where R includes aliphatic and aromatic moieties such as
―(CH₂)n― VII
where n is 1 to 10. -
- Examples of these materials have been previously described above.
- When combining the isocyanates with the diamines, or similarly the carboxylic acids with the isocyanates to produce the polyurea polymer it is preferred that they be combined such that the total aromatic carbon content of the resulting polyurea polymer be 86% or less, preferably 50 to 75%. This is so since polyurea polymers with very high aromatic carbon content tend to be glassy rather than elastomeric in nature and in the practice of the present invention it is desirable for the polyurea membrane to be elastomeric in nature at the temperatures employed in the aromatics saturates separation process.
- The polyurea polymer produced will generally have a molecular weight ranging from about 30,000 to about 150,000, preferably about 50,000 to about 100,000. The maximum molecular weight in reality is set by the necessity of dissolving the polyurea polymer in a solvent in order to facilitate membrane fabrication. Since the higher molecular weight polymers are more difficult to dissolve in any given solvent system, solvation is typically augmented by the application of heat. Since it is a desirable characteristic of these polyurea membranes that they be temperature resistant, it is generally true that the higher molecular weight polymers are preferred for the production of membranes.
- Thus, it is apparent that a compromise must be struck regarding polymer molecular weight. The polymer must not be so high in molecular weight that it becomes insoluble in solvents and thus uncastable into membranes, yet its molecular weight must be high enough so that the membrane which is cast exhibits resistance to elevated temperatures. One solution to this dilemma is to employ a lower molecular weight polymer during the casting procedure and subsequently increase the molecular weight of polymer once the membrane has been fabricated. The molecular weight of the polymer in the membrane can be increased by a post-crosslinking procedure.
- Post crosslinking, crosslinking practiced after the polyurea membrane has been produced can be accomplished by employing thermal or chemical means familiar to the art. Chemical crosslinking is accomplished by adding formaldehyde or additional diisocyanates, said crosslinking techniques being familiar to those skilled in the art.
- Membrane thermal stability is also affected by the degree of aromaticity of the polymer and by the degree of hydrogen bonding. However, since polymer aromaticity is generally set at the time of polymerization and since high aromaticity produces a membrane of a glassy nature, it is apparent that the simplest way in which to produce high temperature stable membranes involves the post crosslinking step.
- When producing a thin film composite membrane of polyurea/polyurethane alloy, the components going to make up the individual polymers are those recited above. In such a case the ratio of polyurea polymer to polyurethane polymer is in the range about 5 to about 95 wt% polyurea, preferably about 10 to about 90 wt% polyurea, most preferably about 25 to about 75 wt% polyurea.
- Finally, if one desires to produce the composite membrane consisting of polyurea polymer and polyurea/urethane copolymer, again the components used to produce the polymer and copolymer are as recited above. In such a case the ratio of polyurea polymer to polyurea/urethane copolymer is in the range 10 to 90, preferably 25 to 75.
- The above are presented solely by way of example. Those skilled in the art, with the present teaching before them, can select from the innumerable materials available the various starting materials which upon combination as described herein will produce the desired polymer, copolymer or polymer alloy which can then be used to produce the thin film composite membranes useful for the separation of aromatics from saturates.
- The solvent employed is one in which the copolymer polymer, polymer alloy precursors are soluble but in which the polymer, copolymer or polymer alloys will precipitate to form a dispersion of fine particles but which will not dissolve or otherwise unduly weaken the thick, porous support layer upon which the dispersion is deposited.
- Examples of such solvent include 1,4-dioxane, ketones (e.g. acetone, methyl ethyl ketone), aromatics (e.g. toluene, xylenes) cellosolve acetate, tetrahydrofuran.
- Examples of useful support layer materials include, polyolefins such as polyethylene, polypropylene etc., teflon, polyesters, nylon, non woven fiberglass, polyimides, polyamides, polysulfones, polyacrylonitriles, and polybenzimidazoles.
- These supports can be of any imaginable physical shape including sheets, tubes, fibers etc. The thin active layer may be deposited on either the inner or outer surface of such tube or hollow fiber support. In operation, the feed to be separated preferably will be contacted with the thin active layer face of the composite membrane.
- Due to the extreme thinness of the selective polymer, copolymer or polymer alloy layer the composite membrane exhibits extremely high flux while maintaining a very high level of selectivity.
- The thin film composite membranes are useful for the separation of aromatics from saturates in petroleum and chemical streams, and have been found to be particularly useful for the separation of large substituted aromatics from saturates as are encountered in heavy cat naphtha streams. Other aromatics containing streams which are suitable feeds for separation are intermediate cat naphtha streams boiling in the 93°C-150°C (200-320°F) range, light aromatics/saturates streams boiling in the C₅-150°C (C₅-300°F) range, light cat cycle oil boiling in the 205-343°C (400-650°F) range as well as streams containing benzene, toluene, xylene or other aromatics typically encounter in chemical plant processes. The separation techniques which may successfully employ the membranes of the present invention include perstraction and pervaporation.
- Perstraction involves the selective dissolution of particular components contained in a mixture into the membrane, the diffusion of those components through the membrane and the removal of the diffused components from the downstream side of the membrane by use of a liquid sweep stream. In the perstractive separation of aromatics from saturates in petroleum or chemical streams (particularly heavy cat naphtha streams) the aromatic molecules present in the feed-stream dissolve into the membrane film due to similarities between the membrane solubility parameter and those of the aromatic species in the feed. The aromatics then permeate (diffuse) through the membrane and are swept away by a sweep liquid which is low in aromatics content. This keeps the concentration of aromatics at the permeate side of the membrane film low and maintains the concentration gradient which is responsible for the permeation of the aromatics through the membrane.
- The sweep liquid is low in aromatics content so as not to itself decrease the concentration gradient. The sweep liquid is preferably a saturated hydrocarbon liquid with a boiling point much lower or much higher than that of the permeated aromatics. This is to facilitate separation, as by simple distillation. Suitable sweep liquids, therefore, would include, for example, C₃ to C₆ saturated hydrocarbons and lube basestocks (C₁₅-C₂₀).
- The perstraction process is run at any convenient temperature, preferably as low as possible.
- The choice of pressure is not critical since the perstraction process is not dependent on pressure, but on the ability of the aromatic components in the feed to dissolve into and migrate through the membrane under a concentration driving force. Consequently, any convenient pressure may be employed, the lower the better to avoid undesirable compaction of the porous backing.
- If C₃ or C₄ sweep liquids are used at 25°C or above in liquid state, the pressure must be increased to keep them in the liquid phase.
- Pervaporation, by comparison, is run at generally higher temperatures than perstraction and relies on vacuum on the permeate side to evaporate the permeate from the surface of the membrane and maintain the concentration gradient driving force which drives the separation process. As in perstraction, the aromatic molecules present in the feed dissolve into the membrane film, migrate through said film and reemerge on the permeate side under the influence of a concentration gradient. Pervaporative separation of aromatics from saturates can be performed at a temperature of about 25°C for the separation of benzene from hexane but for separation of heavier aromatic/saturate mixtures, such as heavy cat naphtha, higher temperature of at least 80°C and higher, preferably at least 100°C and higher, more preferably 120°C and higher should be used, the maximum upper limit being that temperature at which either the membrane is physically damaged. Vacuum on the order of 1-50 mm Hg is pulled on the permeate side. The vacuum stream containing the permeate is cooled to condense out the highly aromatic permeate. Condensation temperature should be below the dew point of the permeate at a given vacuum level.
- The membrane itself may be in any convenient form utilizing any convenient module design. Thus, sheets of membrane material may be used in spiral wound or plate and frame permeation cell modules. Tubes and hollow fibers of membranes may be used in bundled configurations with either the feed or the sweep liquid (or vacuum) in the internal space of the tube or fiber, the other material obviously being on the other side.
- Most conveniently, the membrane is used in a hollow fiber configuration with the then active layer in the outer surface. Feed is introduced on the exterior side of the fiber, the sweep liquid flowing on the inside of the hollow fiber to sweep away the permeated highly aromatic species, thereby maintaining the desired concentration gradient. The sweep liquid, along with the aromatics contained therein, is passed to separation means, typically distillation means, however, if a sweep liquid of low enough molecular weight is used, such as liquefied propane or butane, the sweep liquid can be permitted to simply evaporate, the liquid aromatics being recovered and the gaseous propane or butane (for example) being recovered and reliquefied by application of pressure or lowering of temperature.
- The present invention will be better understood by reference to the following Examples which are offered by way of illustration and not limitation.
- A suspension containing a polyurea/urethane polymer is prepared as follows: Two hundred forty-one grams (0.125 mole) of polyethylene adipate (MW = 1928) and 62.5 grams (0.250 mole) of 4,4′diisocyanato-diphenylmethane were added to a 1 liter resin pot equipped with a stirrer and drying tube. The temperature was raised to 95°C and held for 2.75 hours with stirring to produce an isocyanate-capped prepolymer.
- A stock solution was prepared from this prepolymer as follows: three point three nine (3.39) grams of the above prepolymer was added to 42.785 grams of 1,4-dioxane to produce a solution containing 7.34 wt.% prepolymer. Exactly 3.00 grams of this stock solution (0.0000906 moles of prepolymer) were placed into a 25 ml bottle. A second stock solution containing a diamine was prepared as follows. Exactly 0.746 grams of 4,4′-diamino-diphenyl methane (MDA) were added to 8.3641 grams of 1,4-dioxane and dissolved forming a solution of 0.884 wt% diamine.
- To the bottle containing the prepolymer solution were added exactly 2.0764 grams (0.0000928 moles) of the MDA solution and an additional 6.9838 grams of dioxane and the contents of the bottle were stirred overnight whereupon a translucent suspension of polyurea/urethane was formed. The concentration of this suspension was 1.98 wt% in dioxane.
- A thin film composite membrane was formed as follows. A piece of polypropylene microporous material (Celgard 2500) having an approximate pore size of 0.04 micron was clamped into a frame so that only one side would be exposed to the coating suspension. The 1.98 wt% suspension from Example 1 was poured onto the Celgard and allowed to stand for approximately one minute; whereupon it was poured off. The membrane was placed in a vertical position to allow excess suspension to run off. The procedure was repeated a second time after the dioxane had evaporated from the first application. Contact time for the second application was only 30 seconds. The film was allowed to dry overnight.
- This composite membrane possessed a Urea Index of 50, a functional group density (Σ CO+NH/1000 g polymer) of 13, C=O/NH ratio of 4.67 and an aromatic carbon content of 25.5%
- In order to evaluate the performance of the membrane from Example 2, a perstraction test was carried out in the following manner. Approximately 350 ml of model feed A was placed into the right hand side of the apparatus shown in the attached figure. The membrane to be tested was then clamped between this section and the sweep chamber which was approximately 3 mm deep. The coated side was positioned facing the sweep chamber. The feed was stirred magnetically and heated to the desired temperature. Sweep liquid was distilled from the permeate receiver and recirculated by gravity through the sweep chamber thus carrying away permeate. The sweep liquid was typically chosen to be an alkane that was much lighter than the feed for ease of separation. Samples were withdrawn from the permeate receiver as a function of time and analyzed chromatographically to determine the change in concentration as a function of time.
Model Feed A Component Weight 1 4-xylene 9.97 1,3,5-trimethylbenzene (mesitylene) 10.16 1-decane 20.91 n-decane 31.75 1,2,3,5,-tetramethylbenzene (isodurene) 9.60 naphthalene 8.49 pentamethylbenzene 9.12 100.00 - For comparison, a dense film membrane of the same polymer composition was prepared in solution in dimethylformamide and cast onto a glass plate using a casting knife. The thickness of this membrane as measured by SEM was 11.5 µm.
-
- As can be seen, the membrane that is prepared by the process of the current invention has seven times the flux at the same selectivity as one prepared from a true solution.
- The active layer of the composite membrane of Example 2 was about 2 µ by SEM.
Claims (6)
- A method for producing a thin film composite membrane having a thin active polymer layer of polyurea/urethane on a porous support layer, comprising depositing the thin active layer on the support from a dispersion-suspension of polymer in solvent, the polymer being present in the dispersion-suspension at a concentration of from 0.5 to 10 wt% polymer.
- A method according to claim 1, wherein the polyurea/urethane layer has a urea index, defined as the percentage of the total of urea and urethane groups which are urea, of at least 20% but less than 100%; an aromatic carbon content, expressed as a percent of the total carbon in the polymer, of at least 15 mole percent; a functional group density, defined as the total of C=O and NH per 1000 g of polymer, of at least 10; and C=O/NH ratio of less than 8.
- A method as claimed in claim 1 or claim 2, the dispersion suspension of polymer in solvent is produced by synthesizing the polymer in the dispersing solvent.
- A method according to any proceeding claim, wherein the porous support layer is selected from polyamide, polyimide, polyacrylonitrile, polybenzimidazole, cellulose acetate and polyolefins.
- A method for separating aromatics from feeds which are mixtures of aromatics and non-aromatics with the aid of a membrane, by selectively permeating the aromatic hydrocarbon through a thin membrane; characterised by employing a thin composite membrane having a thin active polymer layer of polyurea/urethane deposited on a thick porous layer from a dispersion-suspension containing from 0.5 to 10 wt% polymer; the polyurea/urethane layer possessing a urea index, defined as the percentage of the total of urea and urethane groups which are urea, of at least 20% but less than 100%, an aromatic carbon content, expressed as a percent of the total carbon in the polymer, of at least 15 mole percent, a functional group density, defined as the total of C=O and NH per 1000 g of polymer, of at least 10, and a C=O/NH ratio of less than 8.
- A method as claimed in claim 5, wherein the separation is performed under pervaporation or perstraction conditions.
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
US108819 | 1987-10-14 | ||
US07/108,819 US4861628A (en) | 1987-10-14 | 1987-10-14 | Thin film composite membrane prepared by suspension deposition |
Publications (3)
Publication Number | Publication Date |
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EP0312377A2 EP0312377A2 (en) | 1989-04-19 |
EP0312377A3 EP0312377A3 (en) | 1990-01-31 |
EP0312377B1 true EP0312377B1 (en) | 1993-03-31 |
Family
ID=22324231
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EP88309634A Expired - Lifetime EP0312377B1 (en) | 1987-10-14 | 1988-10-14 | Method of preparing thin film composite membranes by suspension deposition, and use of such membranes |
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US (1) | US4861628A (en) |
EP (1) | EP0312377B1 (en) |
JP (1) | JPH022852A (en) |
KR (1) | KR890006714A (en) |
BR (1) | BR8805318A (en) |
DE (1) | DE3879857T2 (en) |
ES (1) | ES2039638T3 (en) |
MY (1) | MY104340A (en) |
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US5045206A (en) * | 1990-12-05 | 1991-09-03 | Exxon Research & Engineering Company | Selective multi-ring aromatics extraction using a porous, non-selective partition membrane barrier |
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US5120900A (en) * | 1990-12-05 | 1992-06-09 | Exxon Research And Engineering Company | Integrated solvent extraction/membrane extraction with retentate recycle for improved raffinate yield |
US5095171A (en) * | 1991-04-08 | 1992-03-10 | Exxon Research And Engineering Company | Control of oxygen level in feed for improved aromatics/non-aromatics pervaporation (OP-3602) |
US5254795A (en) * | 1992-10-07 | 1993-10-19 | Exxon Research And Engineering Company | Removal of 2-ring aromatics from low boiling streams containing low concentrations of same using membranes |
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-
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- 1988-10-14 KR KR1019880013410A patent/KR890006714A/en not_active Application Discontinuation
- 1988-10-14 MY MYPI88001153A patent/MY104340A/en unknown
- 1988-10-14 ES ES198888309634T patent/ES2039638T3/en not_active Expired - Lifetime
- 1988-10-14 BR BR8805318A patent/BR8805318A/en not_active Application Discontinuation
- 1988-10-14 DE DE8888309634T patent/DE3879857T2/en not_active Expired - Fee Related
- 1988-10-14 EP EP88309634A patent/EP0312377B1/en not_active Expired - Lifetime
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CHEMICAL ABSTRACTS vol. 84, no. 24, 14 June 1976, page 318, column 1, abstract no. 16969e, Columbus, Ohio, USA; KABASSO et al.: "Trace organic contaminants in drinking water". Evaluation of semipermeable membranes and osmotic pumping to achieve concentration" * |
Also Published As
Publication number | Publication date |
---|---|
BR8805318A (en) | 1989-05-30 |
DE3879857T2 (en) | 1993-08-05 |
EP0312377A3 (en) | 1990-01-31 |
US4861628A (en) | 1989-08-29 |
KR890006714A (en) | 1989-06-15 |
MY104340A (en) | 1994-03-31 |
JPH022852A (en) | 1990-01-08 |
DE3879857D1 (en) | 1993-05-06 |
EP0312377A2 (en) | 1989-04-19 |
ES2039638T3 (en) | 1993-10-01 |
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